Circumscribing the problem: the apparent use of brick since the late 19^th century

In Mexico, the architecture of the late 19^th and early 20^th centuries is synthesized under the appellative Porfirian architecture,¹ because it corresponds to the tenure of President Porfirio Diaz (1876-1911), and includes social, economic, and political factors that at the time, so to speak, comprised the spirit of those days and undoubtedly influenced the way of understanding architecture. If one delves a little deeper into the study of architecture during the Porfiriato period, concepts such as eclectic architecture appear,² a search that usually ends up in a myriad of stylistic appellatives that do not help to fully understand the panorama, although they encompass a set of related architectures: “it is therefore a matter of degrees of kinship”,³ as ^{Katzman (1973, pp. 114-115)} points out.⁴

The problem with conceptualizing an architectural phenomenon in an era pigeonholed by the political regime in power is that it does not characterize each of the different objects of study. For example, the temporality of the Porfirian regime is not enough to encompass the universe of eclectic architecture, which developed vigorously during the years of the Revolution and even during a good part of the 1920s. In the same way, the term 19 ^th century architecture, instituted by Katzman, is inadequate because, as Francisco de la Maza asserted, “There are long centuries and there are short centuries [...] As a century, the 19 ^th century was long in France, for example, because it began with the Revolution; it was long in the United States, because it began with its independence. In Mexico, on the other hand, it was short” ^{(De la Maza, 1974, p. 11)}. Neither does the idea of an architecture of the belle époque⁵ completely satisfy the periodization, since that stage came to an end with the beginning of World War I. What happens then with the eclectic architecture of the immediately subsequent period? Is it devoid of historical temporality?

But beyond the stylistic discussion about the school to which it belonged, or its incorporation to a precise historical period, in the early 20^th century there were significant changes in the way of conceiving architecture that, although not definitive, laid the foundations for a different stage, which would begin in the late 1920s and would become evident from the following decade onwards.

This is where the problem under study arises: what happened with the introduction of cement brick in the revolutionary period, with the occurrence of an accumulation of minor technical advances that have not been pertinently studied. Therefore, there is an area of opportunity to discuss the role played by cement brick in the transition from the revolutionary period in Mexico towards 1930, specifically in Mexico City.

Purpose

The purpose of this study is to determine the historical importance of cement brick-which has a standard size of 20 x 10 x 6 cm⁷ (Figure 1)-within the revolutionary period (1910-1920) and to discuss the information gathered to argue about its implications in the history of housing construction in Mexico City. This study is also intended to evaluate the physical mechanical characteristics of cement brick to have more elements of analysis and, thus, to clarify why it fell into disuse after only 10 years of age.

(Photograph: Alejandro Leal & Alberto Muciño, 2020; source: Authors’ Collection)

Figure 1 Facade in exposed brick in the house Pomona No. 38, Roma Norte, Mexico City. The use of two types of brick in a polychromatic composition is observed, Huerta brand industrialized red brick (22 x 10 x 6 cm) and cement brick (20 x 10 x 6 cm) smooth with bevel. Work attributed to architect Manuel Cortina García. 

Research network

At the end of the 19^th century in Mexico City architecture-primarily in housing-apparent partition walls of brick⁸ began to be used more frequently. This eclectic type of architecture used it as a constitutive and ornamental element in walls, although mainly in exterior facades. Its use, starting from complex brickwork that formed geometric and polychromatic patterns (Figure 1), represented a modern form of construction that set apart the conventional use of brick in construction (this consisted mostly of mixed adobe or tepetate walls with brick at corners and framing as reinforcement, often using plastered or veneered finishes). The development of brick architecture, particularly the one that apparently implemented the use of industrialized brick,⁹ known at the time as compressed brick ^{(Ladrillera La Huerta, 1923, n. p.)}, represented both the beginning of a change in the way of building¹⁰ that left behind the idea of the veneered slats, and a technical advance in terms of the characteristics of the bricks used (Figure 2).

(Photographs: Alejandro Leal & Alberto Muciño, 2020; source: Authors’ Collection)

Figure 2 Two types of cement bricks (20 x 10 x 6 cm). Left, detail of smooth partition wall rigging with bevel; right, detail of grotesque partition wall rigging with bevel. 

As this architectural trend developed, bricks were perfected, going from conventional or common handmade red bricks to industrial bricks, with precise characteristics in terms of their physi comechanical properties.¹¹ Likewise, the idea of the thick mixed wall was abandoned in favor of more slender walls of a single manufacturing ^{(Chanfón, 1998, p. 366)}.

The use of cement brick in domestic architecture-traditionally seen as a minor genre of that art-became unusually relevant at the end of the 19^th century, gradually becoming the protagonist of architectural discussion as well as the recipient of many of the technological advances in construction. That is why this genre is particularly transcendental for a more complete understanding of the history of architecture in Mexico City, since it reveals clues of a change, mainly material, in the way of building architecture. It is in this scenario where the apparent use of brick comes in.

Therefore, it is questioned why cement brick does not appear in the study of the revolutionary architecture (1910-1920) as an important element if it meant a change in the way of building and was the object of study and improvement in its elaboration and use.

As cement brick is an artificial material resulting from a technified production, it is questioned whether it was a material that complied with the mechanical performance required by the current regulations of Mexico City. Therefore, if studies on the mechanical performance of cement partitions used in housing construction in the early 20^th century are established, significant information could be obtained that would contribute to the assessment and development of a line of research in technified materials and add information that would place cement partitions walls as a material of importance in Mexico’s revolutionary architecture.

Adjustment or conformation of a framework of reference

To learn about the mechanical behavior of cement brick under axial compression, in 2021 a study was carried out on samples at the Laboratorio de Materiales y Sistemas Estructurales (LMSE, Laboratory of Materials and Structural Systems) of the Facultad de Arquitectura (FA, Faculty of Architecture) of the Universidad Nacional Autónoma de México (UNAM, National Autonomous University of Mexico), in which the physical mechanical characteristics were measured (Figure 3). The mechanical analysis of cement bricks not only shed new light on the reasons why it was used so frequently in that period, but also provided elements to explain its permanence over time since today we can still observe it in countless facades in Mexico City’s downtown area and in most of urbanizations¹² that were developed at the beginning of the 20^th century, in what are now the neighborhoods known as Condesa, Roma Norte, Juárez, San Rafael, Santa María la Ribera, Doctores, San Pedro de los Pinos, Del Carmen Coyoacán, etcetera.¹³

(Photograph: Alejandro Leal & Alberto Muciño, 2020; source: Authors’ Collection)

Figure 3 Sample of a cement partition wall (20 x 10 x 6 cm) smooth and with bevel, extracted in 2020 from the facade of the house located at Pomona No. 38, col. Roma Norte. 

Study of the physical mechanical properties of cement brick

The pieces called cement brick are made with mortar, and in order to know their physical mechanical properties today (2023) and, therefore, to observe if mortar strength is preserved based on the current regulations, pieces were extracted from the building lo cated at 38 Pomona Street in the Roma Norte neighborhood, in the Cuauhtémoc district of Mexico City, which had an average size of 6.45 x 10.32 x 15.05 cm.¹⁴ It was decided to extract at least six of them, to test them under simple compression, selecting those with a more uniform geometry. These pieces were prepared for compression testing according to the parameters established by Mexican Standard ^{NMX-C-038-ONNCCE-2013 (Norma Mexicana, 2013)}, and because of the cubic geometry of the specimen, three measurements of length, width and height were taken for each piece, to average the values obtained (Figure 4).

(Photographs: Alejandro Leal & Alberto Muciño, 2021; source: Authors’ Collection)

Figure 4 Three images showing the preparation process of the piece, in 2020. To acquire the compressive strength, a load was applied at a constant speed and parallel to the longitudinal direction of the specimen, recording the maximum load at failure (Fult), like what has been done by other researchers. 

As mentioned above, the mechanical tests were carried out at the LMSE. For the compression tests, an Instron^® machine^, model 400RD, with a capacity of 200 t, was used, which is built with a data acquisition system for obtaining real-time graphs, with a displacement sensitivity of 0.05 mm/s (Figure 5). To calculate maximum compression stress (σult), the expression σ_ult= F_ult/A was applied and true stress (σVer) of each test was recorded.

(Photograph: Alejandro Leal & Alberto Muciño, 2021; source: Authors’ Collection)

Figure 5 Instron® compression testing machine, model 400RD, capacity 200 t. 

After performing mechanical compression tests with the maximum load applied, the relevant equations were carried out to show the maximum stress to strength, obtaining the following results (Figure 6).

(Graph: Alejandro Leal & Alberto Muciño, 2021)

Figure 6 Graph of the maximum compressive strength of the samples extracted and prepared according to Mexican Standard ^{NMX-C-038-ONNCCE-2013}. 

According to Mexican Standard ^{NMX-C-486-ONNCCE-2014}, Mortar for Structural Use ^{(Norma Mexicana, 2014)}, mortars are classified depending on their strength capacity: Type I, Type II, and Type III. The standard indicates that to implement mortars in non-structural walls (partition walls), Type II and Type III mortar mixes must be designed, while structural walls must have Type I and Type II mortar mixes. Based on the experimentation carried out, it can be observed that, for the most part, the samples of pieces of brick that were extracted exceed, in accordance with current Mexican regulations, Type II and Type III mortar strengths, and are above 110 kg/cm² in average strength, which shows that they currently meet the standard, that is, they are in a suitable state of construction.

Argumentation

Although brick is a material that has been present throughout the history of architecture, it gained singular importance in France, Belgium, the Netherlands, Germany, and the United Kingdom in the last quarter of the 19^th century, when its industrialized manufacture began. The French influence would be decisive ^{(De la Maza, 1974, p. 49)}, with the publication of books such as La brique ordinaire de ^{Lacroux (1878)} (Figure 7) and the promotion of new methods and patents of the time at fairs and universal exhibitions.

(Source: Jean Lacroux, 1884)

Figure 7 Plate 12 from the book La brique ordinarie. 

As for the traditional way of building walls in Mexico City, “from the middle of the [19^th] century, the construction of brickwork made of reburned brick and blocks of tepetate, a saw-cut natural stone (pumiceous or calcareous tuff), became very popular” ^{(Prado, 1988, p. 309)}. Although the trend was previous to the European one and does not coincide completely with it-mainly because of the use of mechanized bricks-,¹⁶it focused on smaller architectures, often of a domestic nature, which set a precedent in the use of traditional brick in an apparent form in such a type of architecture and, surely, it would be behind the reason for its later and comprehensive use in the housing genre, without tepetate but with industrialized bricks.

The above gives an idea that, although it grew, the use of cement brick did not cease to be relatively limited, since in Mexico the use of traditional brick persisted over mechanized brick. In fact, also in use was the so-called orange brick, of inferior quality to colorado (red) brick, mainly due to a shorter burning time and basically using it as a filling since it was a material completely lacking in characteristics that would allow a structural function ^{(Téllez, 1904, p. 186)}. In this regard, Katzman pointed out that, although brick was profusely used in viceregal architecture, it is more commonly found as a floor and wall covering and very rarely as a structural component; and he continues: “otherwise it would have been difficult for Engineer Besssosi to affirm, without being criticized, that the building he constructed in 1840 for the Hotel Bella Unión was the first to be made of brick in Mexico” ^{(Katzman, 1973, pp. 247-248)}.

Final substantiation

The cement brick stage, 1908-1933

Towards the end of the first decade of the 20^th century, the use of bricks produced in alternative ways to traditional brick became widespread and, mainly, new materials were incorporated, such as cement. This marked a second moment in the use of apparent brick in Mexico City (Figure 8). It should be noted that at the beginning of the 20^th century, the use of reinforced concrete was being developed concurrently in the country, and, like industrialized brick production, it was conceived from experimental practice based on tests outlined by the scientific method. This is the reason why cement brick is a significant material, because it managed to combine the benefits of brick construction with the values attributed to the novel material that entered the scene, called cement, witnessing the process of implementing a technological innovation ^{(Arthur, 2009, p. 146)} -in this case, Portland cement-in which, prior to the extensive use of reinforced concrete, the new material was used more widely through already known construction methods, as was the case with the erection of masonry brick walls and not through reinforced concrete columns, beams, and slabs.

(Photographs: Alejandro Leal & Alberto Muciño, 2021; source: Authors’ Collection)

Figure 8 The dates of these two photographs comprise the first and last dates found in the field (in 2021) that verify the use of cement partition walls in Mexico City. Left, authorship signature of architect Auguste Leroy dated 1908; right, authorship plaque of builder Alberto J. Nunes dated 1933. 

The change or shift in the use of other materials for facades, such as industrialized brick and especially cement brick, gained importance in housing, but not in other construction genres, which were still considered inadequate for this material. A singular example of the impact of cement brick outside the housing realm was in the hydraulic infrastructure works in Mexico City (1903-1913), particularly in the Casas de Bombas ^{(Euroza, 2021, p.40)}. How ever, in general terms, the ideal-concerning the social status and the symbolic value that this material provided to the architecture that was finished in this way-of a mixed construction covered with quarry stone persisted, leaving the resource of integral plastering as the most economical. Therefore, we cannot disregard brick’s technical and economic implications in cons truction or the social and cultural ones.¹⁷

In this sense, how can we explain such a limited way in which cement brick architecture flourished during a certain period in Mexico City? The answers can vary: from the economic and practical sense of using a standardized material, through the local production of Portland cement, to subjective aspects, such as a taste for new facades, for the publicity around cement and its material qualities; and even a moral sense, by betting on the value of austerity. A preference for building using brick and not ostentatiously using stone, during the revolutionary period and in the years immediately following. In any case, everything points to a change in constructive sensibility and a strategy centered on domestic architecture as well as a particular social sector made up of the popolo minuto.

Discussion

The generalized study of revolutionary architecture linked to Porfiriato period disregards the importance of introducing cement brick as a construction resource.¹⁸ This type of brick involved a novel material, such as Portland cement, to produce a mortar mixture.

In the axial compression tests of cement bricks, the main difference in strength was found in that one of the pieces exceeded 180 kg/cm², which may reflect that the industrialization of construction in the masonry sector initially sought high strength, without knowing too precisely either the mix design or the science of the materials to reach a certain value.

It is worthwhile noting that mortar strength is given by the cement technology as well as by the fine aggregates (sands) that compose it; nevertheless, after almost a century of permanence, mortars continue conserving suitable strength for buildings, which attests to the quality of the materials used and the correctness of the mixtures.

The field of research is open for future investigations and for studying the aggregates that compose these mortars by means of mineralogical analyses, since probably the interaction of sands with cement modifies the mechanical strength of the mortars, an important characteristic or variable to consider in the duration and permanence of the materials over time.

However, the limited literature on the mechanical properties of cement brick and its constant comparison with traditional brick are possible causes for the dismissal of the former for larger works. It is argued that the cement technology used during the revolutionary era in Mexico was more widely used in bricks and not in columns or beams, and that, although bricks could have adequate mechanical strength, they alone would not solve designs requiring spans, which are often demanded in public works buildings. Despite its outstanding mechanical performance, this pigeonholed cement brick into architectural genres such as housing.

Final considerations

The use of brick at the beginning of the 20^th century represented a continuity of the accepted values of the time in favor of hygiene and safety, and the bet on non-combustible materials (stairs, floors and ceilings: the use of the Catalan vault instead of Franciscan ceiling). Hence, brick represents a process in tune with the ideals of the late 19^th century and Porfiriato itself. Although the buildings had a mixed construction, they were intended to be provided with the values that cement brick represented, through meticulous plastering that emulated the facades of apparent cement brick (Figure 9). In parallel, in the 1920s, these same ideas, together with the importance of simplifying construction processes, would lead to the widespread use of reinforced concrete as the preferred material in the industry and would represent the end of the apparent brick stage in Mexican architecture.

(Photograph: Alejandro Leal & Alberto Muciño, 2021; source: Author’s Collection)

Figure 9 Flattened facade that looks like cement partition wall, which verifies that, beyond the technical advancement, there was an aesthetic tendency of the apparent partition wall. 

This rupture would then come with the widespread development of reinforced concrete as the most popular and economical material. Used in conjunction with the construction procedure of confined masonry, it would eventually become, in construction terms, the predominant system, even up to the present day. In addition to having a technical and economic nature, this preference is also a matter of taste, a circumstance that in part determined the abrupt end of the trend in apparent brick architecture in favor of smooth or textured plastered facades that did not emulate brickwork (a very visible aspect in the art deco architecture of the late 1920s). It would also be the reason why historiography has disdained this architecture in apparent brick, on the one hand, by not differentiating it from eclectic architectures built in other ways, and, on the other hand, given the idea that all eclectic architecture is synony mous with Porfiriato and the 19^th century; finally, apparent brick architecture was overshadowed by the Revolution that reinforced concrete represented and the triumphant idea of modernity that it embodied.